1. Field of the Invention
This invention is generally directed to vehicle safety restraint systems including shoulder and lap seat belts and more particularly to such restraint systems that include a buckle that houses oppositely biased locking or latching mechanisms that are operable to resiliently engage a locking tong of a latch plate as the latch plate is inserted within the buckle. The latching mechanisms prevent release of the latch plate due to inertial forces created during a vehicle accident, such as a vehicle roll-over. The latch plate can only be released by manual operating a slide release member which cause the simultaneous movement of the latching mechanisms in opposite directions relative to one another to positions wherein the locking tong of the latch plate is no longer engaged.
2. Description of Related Art
Body restraint systems including seat belts, lap belts, shoulder harnesses and the like have been credited with saving numerous lives which otherwise would have been lost in vehicular accidents. The positive benefits obtained due to body restraints systems has been so recognized that, in the United States, the use of seat belts is mandated in all states.
Since their inception, there have been numerous innovative advances made to improve upon the safety and reliability of vehicle body restraint systems. Improvements have been made to the belt and belt materials, the manner in which the belt restraint systems are mounted within vehicles, the manner in which such restraint systems may be automatically adjusted to provide proper tension to suit not only safety standards but to also provide for a measure of passenger comfort and further to improve upon the security of the locking devices and belt buckles associated with such systems.
Most conventional vehicle body restraint systems incorporate a belt which either crosses in front of the lap or diagonally across the body of the vehicle operator or passenger in such a manner as to not adversely interfere with a region of an individual's neck. Belts are retained by latching assemblies including belt buckles into which latch plates carried by the belts can be inserted so as to automatically become locked to the buckles which are normally anchored relative to vehicle frames.
Conventional systems generally utilize two types of release mechanisms for allowing latch plates to be removed from buckle housings such that drivers and passengers can disembark vehicles. A first or side release system includes an operating release button which is generally resiliently urged outwardly at an angle which is perpendicular to an axis or line of insertion of the latch plate into a buckle housing. A second type of conventional release system is known as an end release system and includes an operating lever or button for releasing the latch plate from the buckle housing and which lever is mounted at an end of the buckle housing.
Currently, virtually all types of latching mechanisms for body restraint systems in automotive vehicles are subject to premature release when subjected to at least one mode of inertial force which can be created under various conditions resulting from collisions, roll-overs and other types of loss of vehicle control. Side release latching assemblies or mechanisms, referred to as Type 1 and Type 6 in the industry, will inertially release when subjected to lateral forces which are applied to a backside of a buckle during a vehicle collision or roll-over. Such latching assemblies will also release by the release buttons being forcibly engaged by an object in a vehicle accidently depressing the buttons during an accident, collision or roll-over, thereby prematurely destroying the effectiveness of the restraint systems which can cause severe or deadly injury to persons using the systems.
By way of example, if a person's hip strikes the backside of a buckle frame during an accident, the interior latch which engages a latch plate of a seat belt can and will release when the striking force level is sufficient to cause the inertia of the latch mass, relative to the acceleration and displacement of the buckle frame, to compress a leaf spring and unlatch the buckle.
End type release latching systems will inertially release due to the mass of the release buttons associated therewith when taken into consideration the mass of movement of the latch plate and the direction of rotational release of the latch plate when subjected to an upward or upward and lateral force opposite the locking direction of a latch dog associated with such a mechanism, especially during vehicle roll-overs. This upward or upward and lateral mode of failure occurs when an occupant is more apt to be ejected from a vehicle and thus can result in severe bodily injury or death.
An example of end release latching system for seat belts is disclosed in U.S. Pat. No. 4,358,879 to Magyar. The system uses a release button which is pushed down to release the latch plate as opposed to being pushed laterally as in the side release systems.
Virtually all end release buckles, generally referred to as Type II buckles, operate using an over-the-center mechanism so the actual latch uses either a fairly weak compression spring or a leaf spring for a latching force. A so called “lock for the latch” is a rod or bar that follows an “L” shaped track where the lock bar moves laterally across the buckle frame in a direction of latch movement and then moves vertically along a leg of the “L” and behind the latch after the latch goes over-the-center to its latched position. This movement supposedly locks the latch from moving laterally from lateral forces acting on the buckle frame that would inertially move the latch laterally relative to the buckle frame.
However, the end release buckles have a release button, release slider, lock bar (pin) latch and two compression springs, all of which have mass. One spring actuates the latch laterally and the other spring acts against the latch plate to keep a locking edge in contact with the latch surface or “dog” and applies an upward force against the release button. This spring also acts to eject the latch plate from the buckle when the latch button is depressed and the latch is disengaged.
When vertical forces, or forces with enough vertical component on a buckle, such as forces created by impacts to a bottom of a vehicle in a roll-over, are sufficiently high enough, the buckle latch will release. The design of these buckles is such that both a vertical (longitudinal) and horizontal (lateral) component of force will cause a premature release. In many cases, a vertically upward forces causes an equally vertical downward inertial force to the release button and related components, which causes them to move in a downward (release) direction due to their mass and acceleration relative to the buckle frame. When the components of the release mechanism approach an elbow of the locking “L” slot, the locking pin or bar follows the path of the slot and releases the latch and the compression spring against which these inertia forces are acting, and ejects the latch plate.
The forces acting on a latch plate/buckle assembly that create inertia forces in a release direction come from various and foreseeable sources and directions and always follow Newton's Law. Some of these are:                a) vertical to horizontal forces acting on a vehicle and thus a buckle assembly from impact to the ground during vehicle roll-overs;        b) vertical to horizontal forces acting on a vehicle and thus on a buckle assembly from impact to the vehicle from another vehicle, fixed object or other movable object within a path of the vehicle;        c) vertical to horizontal forces acting on a buckle assembly by objects within the vehicle, such as occupants or loose objects;        d) vertical to horizontal forces acting on a buckle assembly from it being driven into objects within the vehicle, such as a center console between a driver and a passenger or between vehicle occupants; and        e) vertical to horizontal forces acting on a latch plate and release mechanism mass from impulses resulting from emergency management loop release as well as harness mounted air bags and the like where tension on a harness/lap belt webbing is suddenly tightened or released causing a large, near longitudinal impulse force into the buckle, latch plate and release mechanism mass sufficient to cause an acceleration of the mass of the release mechanism parts to develop an inertia force exceeding a release mechanism spring force acting against a release mechanism mass.        
A latch plate weighs anywhere from approximately two (2) to five (5) ounces, depending on whether it is a slip, partial slip or slip lock latch plate. A weight (mass) of the release components of the buckle (button, slider, locking pin, etc.) is a fraction of the latch plate weight.
The dynamic problem with the end release buckles is that when there is an upward force or upward component of force acting on the buckle or a downward impulse from sudden tensile loading/unloading of seat belt webbing through the latch plate, the latch plate mass applies a downward inertia force or impulse that drives an unlatch mechanism downward toward an unlatch position, accelerating the unlatch mechanism masses downward and thus causing the latch to release. Any horizontal or lateral force acting on the buckle frame in an opposite direction to the unlatch direction compounds the unlatching due to acceleration forces acting on the buckle frame.
The above modes of failure are inherent in virtually all conventional side and end release latching mechanisms of conventional vehicle restraint systems. The side release buckle systems are generally simpler and have fewer moving parts and thus are more economical to construct and to install, whereas the end release systems are more complex having multiple moving parts and are thus more expensive to manufacture.
In view of the foregoing, there remains a need to further improve upon the reliability and effectiveness of vehicle body restraint safety belt systems to ensure that the latching mechanisms associated therewith cannot be accidently released during substantially any type of vehicular movement caused during accidents, collisions or resulting from loss of control of a vehicle, such as by operator error or vehicle equipment failure. There is a further need to provide for improvements in vehicle body restraint systems which permit the latching assemblies to be more reliable and more economical to construct.
In applicants application Ser. No. 10/462,738, the contents of which are incorporated herein, in their entirety, by reference, a safety belt restraint system is described which prevents the release of a latching or locking mechanism of a safety belt restraint system by inertial forces which may be directed against the latching assembly during a vehicle accident. In accordance with the invention, each buckle includes a first latch mechanism including a latch dog which is engageable within an opening in a latch plate as the latch plate is inserted within a buckle housing. The latching mechanism is positively retained in engagement with the latch plate by two equally resisted and oppositely oriented push button release mechanisms. The release mechanisms are connected by a resilient element, such as a spring, such that any force tending to push one of the release buttons inwardly of the buckle to effect a release of the latch plate places an equal and opposite force on the opposite release button to sustain it in a locked position thereby preventing release of the latch plate from the buckle. With this structure, equal and opposite forces must be simultaneously applied to each of the release buttons in order to cause a camming of the latch relative to the latching mechanism to thereby permit withdrawal of the latch plate.
In applicant's application Ser. No. 10/669,381, the contents of which are incorporated herein, in their entirety, by reference, an embodiment of the invention is disclosed wherein latching mechanisms are provided in the form of slide blocks which are positively guided between a pair of fixed guide blocks which define channels therebetween in which the latching mechanisms are reciprocally moveable against a spring or other resilient element which extends therebetween so as to apply equal and opposite biasing force against each latching mechanism. Each of the slide blocks of the latching mechanisms also includes a lock dog which is engageable with bifurcated hooked tongs of a latch plate when the latch plate is inserted within the buckle housing to thereby retain the latch plate in a locked position. The slide blocks further include a tapered camming surfaces which extend inwardly toward a central longitudinal axis of the buckle housing from the lock dogs toward the opposite end of each slide block. In the embodiment, a single longitudinally slidable release member is used to create an equal and opposite force to move the latching mechanisms from their first locked position to their second release position. The forward end of the slide member includes two spaced legs which are designed to cooperatively engage the camming surfaces associated with each of the slide blocks. To release the latching mechanisms from engagement with the locking tongs of the latch plate, the release member is manually urged inwardly of the buckle housing wherein the legs will engage the camming surfaces of the slide blocks thereby simultaneously urging them toward one another against the spring or other resilient element extending therebetween, thereby moving the latching mechanisms to their second release positions.